DE3108536A1 - METHOD AND DEVICE FOR ELECTROEROSIVE WIRE CUTTING - Google Patents

Description

3108538

Inoue-Japax Research Incorporated Yokohamashi, Kanagawaken, Japan

Method and device for electrical discharge machining

The invention relates generally to wire electrical discharge machining and, more particularly, to a new and Useful method and apparatus for wire electrical discharge machining of a conductive workpiece with a continuous wire electrode, which is extended and axially conveyed for continuous Movement between a delivery side and a receiving side is held by a cutting zone in which the workpiece is arranged.

The electroerosive wire cutting process, as it is in the prior art (see, for example, DE-OS 2 721 804) in general

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makes use of a continuous wire electrode, e.g. B. made of copper or brass and a regular thin wire shape, ζ. Β. of circular cross-section, with a diameter in the range between 0.05 and 0.5 mm. The wire is mounted in a wire support system to stand out from a Delivery side, e.g. a wire delivery spool or drum, to a take-up side, e.g. B. a wire take-up reel or drum ^ to extend and is driven axially by drive means, ζ. B. arranged on the receiving side Pull roller system, conveyed to advance along a guided continuous path and continuously to move through a cutting zone. A workpiece arranged in the cutting zone becomes the moving one Facing wire to delimit a machining gap with a machining fluid medium is rinsed. A machining electrical current is passed between the one forming a tool electrode moving wire and the workpiece forming a counter electrode flow to / from the workpiece to be removed. At the same time, the workpiece is generally transverse to the moving wire electrode Axis shifted along a certain path so that a desired wire cutting pattern passed through the Path of the relative displacement is determined, is generated in the workpiece. The term "electroerosive" or "Electrical discharge machining" is used here to describe a machining process in which material is removed as a result of the passage of a high-density electric current that takes the form of a sequence of individual, temporal

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spaced electrical discharges that rait higher Frequency occur, or a strong electrolytic dissolving current, which is either a direct current or can be a pulsed current, or a combination of the effect of electrical discharges with the electrolytic one Can assume dissolving effect, is caused by the machining gap. Depending on the desired special effect of material removal, the machining fluid is suitably composed to to form the dielectric, conductive, or dielectric / conductive gap medium. Water can be deionized or be ionized to various degrees to produce a favorable EDM (electrical machining discharge), ECM (electrochemical machining) or ECDM (electrochemical and discharge machining) liquid medium to build. The gap flushed with the machining liquid must be small in size, generally be on the order of microns in order to reduce the electroerosive gap condition between the moving wire electrode and to create and maintain the workpiece. The constant axial movement of the wire electrode results a continuous renewal of the machining surface attached to the workpiece through the machining gap through, and is needed because the wire electrode must be as thin as mentioned earlier.

The basic principle of wire cut electrical discharge machining is therefore to achieve a desired cutting pattern or to shape the pattern by applying the appropriate pattern or profiling feed between the workpiece and a "line" electrode formed by the wire. This is a fundamental one

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Difference from the sinking-type electroerosion process, in which the tool electrode is specially shaped and reproduces the electrode shape in the workpiece will. In the wire cut electrical discharge machining process, there is no analogy between the profile of the wire electrode and a desired cutting pattern to be formed in the workpiece. The "line" electrode effectively follows a prescribed path in the workpiece that directly generates the desired cutting pattern. Hence the Accuracy of a wire cutting pattern by the accuracy of the prescribed and in the relative movement between the wire electrode and the workpiece followed the profiling feed path influenced. There is no prior art suggestion that the shape of the wire electrode could affect the accuracy of a wire cut pattern in the workpiece. Accordingly, it was generally believed that it is sufficient to use a wire electrode with a circular or regular cross-section, without others are available provided the wire is of sufficient thickness or as thin as 0.05 to 0.5 mm to achieve a desired accuracy, since the accuracy depends on the question of the exact setting of a profiling feed path and depends on the wire electrode following the precisely set path exactly.

The invention is based on the object of a new and useful method and a corresponding one Device for electroerosive wire cutting of an electrically conductive workpiece to develop, which is the wire cutting of a conductive workpiece with greater accuracy.

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The object of the invention, with which this object is achieved, is initially a method for electrical discharge machining Wire cutting a conductive workpiece with a continuous wire electrode extending under and axial conveyance for continuous movement between a delivery side and a receiving side a cutting zone is maintained in which a) the wire electrode with a regular cross-sectional profile from the delivery side, b) the wire electrode leads into the cutting zone, where it continuously a Electro-discharge wire cutting action on the workpiece exercises, and they continue to convey continuously to the receiving side, and c) a relative displacement between the moving wire electrode and the workpiece length a predetermined path to form the desired Causes wire cutting pattern in the workpiece, with the characteristic that the wire electrode is downstream of the Forms the delivery side and upstream of the cutting zone and gives it a cross-sectional profile that of the regular Cross-sectional profile different and related to a cutting pattern to be machined in the workpiece is preselected, and the wire electrode thus formed into the Cutting zone leads.

Refinements of this method are characterized in claims 2 to 7.

Shaping can be done by drawing the wire electrode with the initially regular cross-section through a drawing mold

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-limit an opening of the pre-selected cross-section profile complementary cross-sectional profile to give the wire electrode the preselected cross-sectional profile for conveying into the cutting zone. Alternatively the molding can also be done by electrical discharge machining. One or more auxiliary wire electrodes can be used for this purpose in the required number to form a profiling wire network or -electrode system are mounted in a mutual assignment that corresponds to the preselected Cross-sectional profile. Corresponds to and through which the wire electrode is conveyed from the delivery side and electroerosively machined, so that the wire electrode with the preselected cross-sectional profile for insertion into the cutting zone for machining the workpiece receives. According to a further alternative, the wire electrode can also be shaped by cutting or grinding a cutting or grinding tool.

The invention also relates to a device for carrying out the method according to the invention a wire feed device on the delivery side for feeding the wire electrode with a regular cross-sectional profile, a wire feed device for continuous Conveying the wire electrode into the cutting zone for the purpose of continuous movement thereby under electrical discharge Cutting action on the workpiece and for the continuous further conveyance of the wire electrode to the receiving side and a profiling feed device for the relative displacement of the workpiece with respect to the moving wire electrode along a predetermined path to form the desired wire cutting pattern in the workpiece with which Indicates that downstream of the wire feeder and

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upstream of the cutting zone, a forming device for forming the wire electrode with a cross-sectional profile is arranged, which is different from the regular cross-sectional profile and in connection with an im Workpiece to be machined is preselected.

Refinements of this device are characterized in claims 9 to 15.

For example, the forming device can consist of a drawing forming device which has an opening with one of the preselected Profile has complementary profile and in the path of the feed device from the delivery side conveyed wire electrode is arranged around the wire electrode having the regular cross-sectional profile to pull it and move it to the selected cross

to the
to deform cutting profile before / introduction into the cutting zone by the wire conveyor. Alternatively, the forming device consists of a cutting or grinding tool which is arranged in the path of the wire electrode in order to cut or grind it and thus to provide it with the preselected profile. According to a further alternative, the molding device can consist of an electro-erosion electrode system. For this purpose, one or more auxiliary wire electrodes in the required number can be mounted in such a way that they form a profiling wire network or system which is arranged in a mutual relationship that corresponds to the preselected cross-sectional profile and through which the wire electrode is conveyed from the feed device and processed by electroerosion, around the wire electrode

31Q853S

to give the preselected cross-sectional profile for introduction into the cutting zone by means of the wire conveyor.

The cross-sectional profile produced by the forming device of the wire electrode coming from the feeding device can be triangular, square, semicircular, star-shaped or any other preselected Be a shape that depends on the particular cutting pattern to be machined in the workpiece. Contrary to the prevailing opinion that the thin wire electrode at Wire cut electrical discharge machining of any regular shape available, such as B. of circular shape, can be and that there is no special need, a special one in terms of cutting accuracy Choosing the cross-sectional profile of a wire electrode instead of the commonly available profile found that there are particular advantages to inserting a wire electrode into the cutting zone which is provided with a special cross-sectional profile is formed in connection with a special to be machined in the workpiece Cutting pattern is selected. This has been found to be beneficial in a variety of machining application cases and found effective where the requirements for the sharpness of a corner cut or the smoothness of a Cutting angles are strict and a fine and intricate wire cut pattern is to be made. In addition to the Importance of forming the wire electrode with one in connection with such a wire cutting pattern selected special cross-section profile it was considered as Found extremely useful, this formation in the mounted in an electrical discharge machining wire cutting arrangement Wire stretch to be carried out immediately before the wire enters the cutting zone.

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The invention is explained in more detail with reference to the exemplary embodiments illustrated in the drawing; in this demonstrate:

Fig. 1 (a), 1 (b) and 1 (c) cross-section of optional on the wire electrode of a regular Cross-section profiles to be applied in one step or with a device according to the invention;

Fig. 2 schematically partly in block form and partly in section an embodiment of the device according to the invention, in which a wire electrode fed from a delivery side by means of an upstream of the cutting zone arranged die forming device is formed;

Figure 3 is a cross section of a die assembly system with a plurality of drawing dies, which are optionally movable into one position, in which they have their draw form openings of various shapes in the path of the wire electrode;

Fig. 4 is a schematic view for illustration a plurality of forming wire electrodes for processing the wire electrode in front of their Entry into the cutting zone for the purpose of formation with a desired cross-sectional profile;

Fig. 5 is a cross section of the forming wire electrodes in the process of processing the wire electrode in Fig. 4; and

6 is a schematic sectional view for illustration a wire electrical discharge machine having a plurality of different in cross section Profiles shaped wire electrodes

V.

for machining a single workpiece using the invention.

According to Fig. 2, a continuous wire electrode is held so that it is between a delivery side in the form of a delivery reel 2 and a take-up side in the form of a take-up reel 3 and between this is conveyed axially with continuous movement. The wire electrode 1 is driven by a traction drive unit 4, e.g. B. reel and squeeze rollers, axially supported, driven by a motor and on the side of the Take-up reel 3 are provided. A motor driven wire brake mechanism 5 is on the side of FIG Delivery reel 2 is provided and, in conjunction with the traction drive unit 4, causes a suitable tension in the wire electrode 1 and enables the latter to move through it at a suitable speed. A workpiece 6 is in the wire path between a pair of machining guide bodies 7a and 7b shown arranged. The guide bodies 7a and 7b are provided in order to have a straight path between them set up moving wire electrode 1 to the latter precisely in relation to an electrical discharge machining position of the workpiece 6.

The workpiece 6 is fixedly mounted on a work table 8 which is driven by a pair of motors 9 and 10 which are supplied with drive signals from a numerical control unit 11. An electrical discharge machining power source 12 has a pair of terminals, one of which is connected to the wire electrode via a brush 13 and the other of which is connected to the workpiece 6 via a conductor 14 attached thereto. A nozzle 15 is aligned with the cutting zone in order to introduce a machining liquid 16 into a machining gap,

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which is limited between the moving wire electrode 1 and the workpiece 6. For the purpose of the invention the wire electrode fed from the delivery reel 2 can be of any cross-sectional profile, e.g. B. of circular Be cross-section. In other words, a coil of wire, for example made of copper or brass exists, has a thickness in the range from 0.05 to 0.5 mm and is commercially available, can be used as coil 2. Such a wire is of course of circular cross-section, but may also be available in another one Be form.

In the embodiment according to FIG. 2, the wire electrode 1 with the regular cross-sectional profile formed by a drawing die, so that the wire electrode a preselected cross-sectional profile of a shape as shown in FIGS. l (a), l (b) or l (c) show deviates from the original regular cross-sectional profile. The wire electrode 1 with the regular Cross-sectional profile, which is fed from the dispensing reel 2, is first allowed to run through a heating zone 17, after which it is drawn through a drawing die 18. The drawing mold 18 has an opening of one in Fig. L (a), l (b) or l (c), through which the wire electrode is driven by means of the traction drive unit 4, so that it has the shape of the complementary cross-sectional profile. The drawing form 18 is with a sonic or ultrasonic horn 19 provided, which is fed by a power source to 18 sonic or ultrasonic vibrations on the drawing die to apply and thus to facilitate the pulling of the wire electrode 1. The drawn wire electrode with the deformed cross-sectional profile becomes one

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Cooling zone 20 passed, which is fed from a nozzle 21 with a coolant, so that the wire electrode 1 assumes a greater tensile strength.

The wire electrode 1 with the selected cross-sectional profile is then used as a braking mechanism 5 via rollers guided in order to run into / into the cutting zone delimited between the guide bodies 7a and 7b, where they are in electrical discharge machining position relative to the workpiece emotional. A sequence of processing impulses in an EDM, ECM or ECDM mode of operation or a unidirectional one Directed current in an ECM or ECDM mode of operation is between the moving wire electrode 1 and the Workpiece 6 is placed over the machining gap flushed with the machining fluid medium 16, to remove electrical discharge machining 7 from workpiece 6. For example, when the shaped wire electrode 1 has a triangular cross-section, one of the three wire surfaces, the one corner of one in the workpiece 6 cut-out pattern is suitable, this part electroerosively with a reduced radius center and so can be processed with increased accuracy.

3 shows a versatile draw molding system with a plurality of four drawing molds 18a, 18b, 18c and 18d with mold openings which are shaped as a triangle 18a », square 18b ¹ , star 18c ¹ and circle 18d '. The drawing molds 18a, 18b, 18c and 18d are attached to a disk 22 which can be rotated about a shaft 23 in order to selectively one of the mold openings 18a ¹ , 18b ¹ , 18c ¹ and 18d 'into the path of the wire electrode 1 coming from the Heizzonec-17 bring (Fig. 2)

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The opening la ¹ , if selected, forms the wire electrode 1 into a triangular cross-sectional profile. The opening Ib ¹ , when selected, forms the wire electrode with a square cross-sectional profile. The opening Ic ", when selected, forms the wire electrode 1 with a star-shaped cross-sectional profile. The opening Id ¹ , when selected, forms the wire electrode 1 with a circular cross-sectional profile of reduced diameter. One of these shapes is used in connection with an im Workpiece 6 selected special cutting pattern to be machined in the cutting zone.

Also any of the other common wire forming devices can replace the drawing die device with the drawing die 18 in the arrangement according to FIG. 2. For example, a cutting or grinding tool device can be used to cut the wire electrode 1 mechanical or abrasive with a pre-selected cross-sectional profile to shape.

A preferred molding device, however, makes use of electrical discharge machining. 4 and 5 show an electroerosion electrode device? A_, which is designed for reshaping the wire electrode of regular cross section fed from the dispensing coil 2 into a triangular cross section. The electrode device 2Λ_ has three wire electrodes 25, 26 and 27, each of which has a much smaller thickness than that of the cutting wire electrode and is held on a pair of guide bodies 25a and 25b, 26a and 26b, 27a and 27b, around a moving wire path in between to give. The leadership

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bodies 25a, 25b, 26a, 26b, 27a and 27b are arranged so that that they have a triangular wire network 28 (Fig.5) in the Passage of the wire electrode 1 between a pair of machining guide bodies 30 and 29 in FIG between the delivery reel 2 and the braking mechanism 5 form forming zone provided and the triangular Wire network 28 is traversed by the moving wire electrode 1 in its longitudinal direction. A machining liquid is supplied to the forming zone while an electric current is applied between each of the forming wire electrodes 25, 26 and 27 and the cutting wire electrode can flow in order to machine the latter into a triangular cross-sectional profile by electroerosion. the Number of forming wire electrodes 25 ... and the positions of the associated guide bodies 25a, 25b ... with respect to the Axis of the cutting wire electrode 1 are depending on the particular desired cross-sectional shape of the wire electrode certainly. For example, if a square profile is desired, four processing wires are used, and each pair of them are arranged in parallel with each other with a spacing equal to the side of the square. A semicircle is obtained by using a single machining wire 25, 26 or 27 that is cut from the guide bodies 25a and 25b, 26a and 26b or 27a and 27b is held so that it is the central axis of the cutting wire electrode 1 cuts. Advantages of the EDM machine are ease of adjustment and suitability for molding with practically no mechanical stress.

FIG. 6 shows another wire cutting electrical discharge machining device for machining a single workpiece 6 with a plurality of shaped wire electrodes 31, 32 and

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As in FIG. 1, the workpiece 6 is held firmly on the work table 8 driven by motors 9 and 10. The device contains three machining head pieces 34, 35 and 36 / which are mounted on a shaft 37, the is held firmly between a pair of arms 38 and 39 of a frame 40. Each of the machining headers 34, 35, 36 has parallel arms or protrusions 34a and 34b, 35a and 35b, 36a and 36b, each arm terminates at one end 41a, 41b, 42a, 42b, 43a and 43b, respectively. Arms 34b, 35b and 36b are shown to support Dispensing reels 44, 45 and 46 for feeding one wire electrode 31, 32, 33 each. The wire electrodes 31, 32 and 33 are guided between the arm ends 41b and 41a, 42b and 42a as well as 43b and 43a and are on take-up reels 47, 48 and 49 mounted on arms 34a, 35a and 36a, respectively. The ones on the delivery reels 44, 45 and wire electrodes 31, 32 and 33 stored and discharged by them have a regular cross-sectional profile and forming devices 50, 51 and 52, each of which may be of any of the types mentioned above, are arranged under the workpiece 6 in order to have these wire electrodes 31, 32 and 33 different from the regular profile and, depending on the particular patterns to be worked out in the workpiece 6, preselected cross-sectional profiles to raise. Formers J50, 51 and 52 can be attached to headers 34, 35 and 36, respectively. The headers 34, 35 and 36 can be rotatably mounted on the shaft 37.

In a particular cutting operation, any one or two headers 34, 35 and / or 36 can be combined with the associated molding devices 50, 51 and / or 52

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chosen to be attached to and engaged with the workpiece 6 are arranged. The wire electrode 31, 32 or 33 is taken from the delivery spool 44, 45 or 46, respectively supplied to the selected head piece 34, 35 or 36, passed over the arm end 41b, 42b or 43b and through the Forming device 50, 51 or 52 promoted for reshaping the wire electrode into the preselected cross-sectional profile are suitable. The wire electrode 31, 32 or 33 is then inserted into, through and out of the Cutting zone conveyed to the formed profile in the EDM wire cutting position with respect to the workpiece to bring and so hold, while the latter shifted relative to the wire axis along a prescribed path is, whereby the corresponding cutting pattern in the workpiece 6 with an increased accuracy or a desired property is formed. At the end of the process or when it is found that he in its course a different cutting property in connection with a peculiarity of the cut If the pattern is required, the head piece used is replaced by another head piece and the wire cutting process is continued to create a different cutting pattern or to achieve the same cutting pattern with the of the pattern to another preselected cross-sectional profile shaped wire electrode.

Thus, a new and useful method and apparatus are provided a conductive workpiece available for elektroer _w osiven Drjahtschneiden according to the invention, thereby a desired cutting pattern can be obtained with increased accuracy. The invention

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is particularly advantageous around a corner cut with increased or decreased sharpness as required and obtain extremely complicated cutting patterns in a simplified manner.

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Claims (15)

Expectations 1. / Method for electrical discharge machining of a conductive workpiece with a continuous wire electrode, the extension and axial conveyance for continuous movement between a delivery side and a Recording side is held by a cutting zone in which one a) conveys the wire electrode with a regular cross-sectional profile from the delivery side, b) leads the wire electrode into the cutting zone, where it continuously performs an electrical discharge machining wire cutting action exerts on the workpiece, and continues to convey continuously to the receiving side, and c) a relative displacement between the moved wire electrode and the workpiece along a predetermined one Causes path to form the desired wire cutting pattern in the workpiece, characterized, that the wire electrode is shaped downstream of the delivery side and upstream of the cutting zone and given a cross-sectional profile, that different from the regular cross-sectional profile and in connection with one to be machined in the workpiece Cutting pattern is preselected and the wire electrode thus formed leads into the cutting zone. 2. The method according to claim 1, characterized, that the shaping of the wire electrode by means of drawing through a drawing die with a complementary to the preselected Performs cross-sectional profile formed mold surface. 581- (A968) -TF 310853a 3. The method according to claim 2, characterized in that the wire electrode is heated prior to drawing. 4. The method according to claim 2, characterized in that one shaped with the preselected profile wire electrode cools down. 5. The method according to claim 2 or 4, characterized in that one vibrations of a sound or during the pulling tiberschal! frequency can act on the drawing form. 6. The method according to claim 1, characterized in that the forming of the wire electrode by electrical discharge machining Wire cutting the wire electrode for training of the preselected cross-sectional profile. 7. The method according to claim 6, characterized in that the wire electrode is used for electrical discharge machining supports a plurality of axially moved wire electrodes so that they form electrode surfaces which are of the Wire electrode with the regular cross-sectional profile under electrical discharge forming to the preselected profile be traversed. 130052/0713 3108538 8. Device for performing the method according to one of claims 1 to 7 with a wire feed device on the delivery side for feeding the wire electrode with a regular cross-sectional profile, a wire conveyor for continuously conveying the wire electrode into the cutting zone for the purpose of continuous Movement thereby under electroerosive cutting action on the workpiece and for continuous further conveying the wire electrode to the receiving side and a profiling feed device for relative displacement of the workpiece with respect to the moving wire electrode along a predetermined path to form the desired wire cutting pattern in the workpiece, characterized, that downstream of the wire feed device (2; 2; 4 4, 45, 46) and upstream of the cutting zone a forming device (18; 18a, 18b, 18c, 18d; 50, 51, 52) for forming the wire electrode (1; 1; 31, 32, 33) with a cross-sectional profile is arranged, which is different from the regular cross-sectional profile and in connection with an im Workpiece (6) to be machined cutting pattern is preselected. 9. Apparatus according to claim 8, characterized, that the forming device consists of a drawing-forming device with a drawing mold (18) which is one of the preselected Has cross-sectional profile complementary mold surface. 130052/0712 10. Apparatus according to claim 9,
characterized, that the draw-forming device has a plurality of such drawing forms (18a, 18b, 18c, 18d) with such mold surfaces with different cross-sectional shapes (18a ¹ , 18b ¹ , 18c ·, 18d '), which can be used individually for different preselected profiles and optionally in the conveyor track of the from the wire feed device (2) coming wire electrode (1) are adjustable. 11. The device according to claim 9 or 10, characterized < marked, that it has a heating device (17) arranged upstream of the drawing-forming device (18; 18a-d). 12. The device according to claim 11,
characterized, that it has a cooling device (20, 20, 21). 13. Apparatus according to claim 9, characterized, that they have a vibration device (19) for applying vibrations of a sonic or supersonic frequency has the drawing form (18). 14. Apparatus according to claim 8, characterized, that the molding device consists of an electrical discharge machining device (_24_) consists in the passage of the Wire electrode (1) is arranged from the wire feed device (2). 130052/0712 3105538 15. Apparatus according to claim 14,
characterized, that the electroerosion electrode device (2A) has a plurality of axially moved wire electrodes (25, 26, 27) which are arranged to form electrode surfaces which can be traversed by the wire electrode (1) with the regular cross-sectional profile under electroerosive forming to the preselected profile. 130062/0712